Egyptian state media have closed ranks in support of the military and its version of the removal of President Mohamed Morsi as well as Monday's killing of 55 supporters of the deposed Islamist leader in a shooting at a protest in Cairo.

In an atmosphere of extreme polarisation, the country's state and many independent news organisations are now solidly backing the interim president Adly Mansour, who was installed by the army last week. TV channels sympathetic to Morsi's Muslim Brotherhood have been shut down.

Foreign media outfits perceived as being sympathetic to Islamists are being attacked, with CNN and al-Jazeera TV singled out for hostility. The US news network has been vilified by protesters as being pro-Brotherhood, partly because it described the military's move as a coup.

In one very public display, al-Jazeera Arabic's Cairo director, Abdel Fatteh Fayed and his crew were ejected from an army press conference on Monday after Egyptian journalists in the room chanted "Out! Out!". The Qatari-owned satellite TV network has long been accused of partiality towards Islamists across the Arab world.

Later 22 employees of its Cairo bureau announced their resignation after security forces raided the premises. Wesam Fadhel accused the channel of "lying openly" about events in Egypt. Anchor Karem Mahmoud said the staff had resigned in protest against "biased coverage."

Egypt's state media, led by the veteran al-Ahram newspaper, has not questioned the military's account of what happened outside the Republican Guard officers club on Monday, when the protesters and three security personnel were killed. State TV broadcast few images and none of the harrowing ones seen on social media or foreign channels. The presidency has, however, announced a judicial investigation.

In Tuesday's editions, al-Ahram called the attackers "armed men." Al Gumhouria described them as "terrorists". Al-Akhbar, another state-owned paper, ran front page pictures of soldiers carrying a wounded comrade and an image purportedly showing a protester firing on soldiers.

Following the fall of Hosni Mubarak in February 2011, Egyptian state media first moved to support the military and then, after his election last June, to back Morsi. Al Ahram's current editor, Mamdouh al-Wali, was appointed as part of a process known as the "Brotherhoodisation" of key institutions. He has not been seen at the paper since the president's removal.

The love-in with the new administration marks a complete reversal of the relationship private media organs had with the state under Morsi. Two weeks ago, the government banned the owner of CBC, a major opposition TV channel, from leaving the country, and ordered a leading opposition talkshow host off air. Newspapers backing the army's version of events this week – such as al-Dustour and al-Watan – were only a fortnight ago attacking Morsi every day.

Five pro-Islamist TV channels were targeted moments after the army announced Morsi's removal and remain closed – though journalists who were arrested were released. Half a dozen Egyptian human rights organisations have expressed their deep concern. "The story of the state-owned media is really shameful," said Hani Shukrullah, who was sacked as editor of al-Ahram online this year. "You have the same administration and the same people who before 2011 were defending Mubarak and describing revolutionaries as depraved troublemakers moving to support the military and the revolution and then moving to the Brotherhood once Morsi came to power. Now they are moving back again.

"Now the emphasis is on singing the praises of the army. There are some exceptions and dissenting voices. But the core is becoming quite repulsive. The private TV stations don't tell the story. With the closure of the Islamist stations you really have to turn to CNN or al-Jazeera to see what the Islamists are saying and doing – except the footage of them committing atrocities."